FIGS. 1A-1B show one arrangement of a camera and a display screen in a videoconferencing unit 101. FIG. 1A shows a front view of a display screen 102 displaying an image 103 of the far end participant. Camera 104 is placed on top of the display screen 102 for capturing an image of a near end participant 105. Typically, while communicating, the near end participant 105 will look into the eyes of the far end participant displayed on the display screen 102. The exact location on the display screen 102 where the far end participant's eyes appear may vary; but, generally, they may appear anywhere above the half and below two-thirds of the height of the display screen 102. The camera 104 is however placed at the top of the display screen 102. Therefore, the image of the near end participant 105 captured by camera 104 will appear as if the near end participant 104 is looking downwards. As a result, the far end participants will see the image of the near end participant looking not straight out at them, but undesirably downwards. If the far end videoconferencing unit has a similar setup as shown for the near end videoconferencing endpoint in FIG. 1A, then the image of the far end participant captured by the far end camera will also suffer from the same downward looking feature. In such cases, both the near end and far end participants will not be able to make direct eye contact with the images of the other end. Naturally, this is undesirable.
Note that the downward looking effect gets worse with an increase in the angle α subtended at the eyes of the near end participant 105 by the near end camera and a location on the display screen 102 where eyes of the far end participant are displayed. Angle α is a function of two distances: (i) the horizontal distance between the near end participant 105 and the display screen 102 and (ii) the perceived distance (in a vertical plane) between the camera 104 and the location on the display screen 102 where the far end participant's eyes are displayed. Angle α is inversely proportional to the horizontal distance, i.e., angle α decreases with increase in the distance between the near end participant and the display screen. Further, angle α is directly proportional to the perceived distance, i.e., angle α decreases with decrease in the perceived distance between the camera and the location on the display screen where the eyes of the far end participant are displayed. It will be appreciated by a person skilled in the art that the apparent lack of direct eye contact decreases with the decrease in angle α. Typically, a value of angle α that is less than or equal to approximately 5 degrees is sufficient in rendering the apparent lack of direct eye contact to imperceptible levels.
There are several solutions in the prior art that attempt at solving the above problem of apparent lack of direct eye contact. One such solution is shown in FIG. 2, in which a teleprompter style display and camera setup minimizes angle α. The display screen 102 is placed horizontally over which a half-silvered mirror 107 of substantially same width as the display screen 102 is placed in a manner such that the image displayed on the display screen 102 is reflected off the mirror 107 and visible to the near end participant 105. Camera 104 is placed behind the mirror 107 so that even though the near end participant 105 is visible to the camera 104, the camera 104 itself is not visible to the near end participant 105. Camera 104 is placed at a height at which the eyes of the far end participants are anticipated to appear on the mirror 107 as seen by the near end participant 105. Consequently, the angle α is minimized, and in the image captured by the camera 105 when displayed to the far end participant, it appears as if the near end participant is making direct eye contact with the far end participant. However, the horizontal placement of the display screen 102 and the angled mirror 107 occupy considerable space. Furthermore, the size and weight of the mirror 107 can be quite large, making the videoconferencing system of FIG. 2 bulky.
Another solution is shown in FIG. 3A, in which a rear projection system is modified to provide direct eye contact. In this example, camera 104 is placed behind a rear projection screen 111 having an aperture 110, such that the camera 104 can capture the images of the near end participants in front of the screen 111. A cable 109 connects the camera to a controller 113. Images of the far end participants is emitted by projector 108 onto a mirror 112, which is placed behind the rear projection screen 111 at an angle such that the projected images are reflected by the mirror 112 and projected on the screen 111. The positions of mirror 112 and the aperture 110 are selected such that the images of the eyes/faces of the far end participants appear near the aperture 110. Thus, when the near end participants look at the images of face/eyes of the far end participants on screen 111, they would be also making direct eye contact with the camera 104. As a result, in the captured images of the near end participants, it will appear as if the near end participants is making direct eye contact with the far end participant.
However, the solution depicted in FIG. 3A has a few disadvantages, which are shown in FIG. 3B. FIG. 3B shows a front view of the rear projection system of FIG. 3A. Because the camera 104 and the cable 109 lie in the path of the light rays reflected from the mirror 112, the camera 104 and cable 109 cast a shadow onto the screen 111. For example, shadow 115 can be attributed to the cable 109, while circular shadow 116 can be attributed to the camera 104. Shadows 115 and 116 can be distracting to the near end participants. Thus, such a setup is ill-suited to a videoconferencing unit.